EVs are expected to be widely adopted across the world in future because of their small environmental impact and low maintenance and running costs. These cars can be charged either in an ordinary charging (slow charging) mode or a rapid charging mode. During charging, a trade-off relationship holds between the charging time and the power requirement. The ordinary charging requires less electric power than the rapid charging but takes as long as several hours. Rapid charging, on the other hand, rapidly charges an EV battery in several minutes but requires a large amount of electric power. In order to offset power requirement for EV charging, many charging stations, service stations, charging stations in office buildings, plants, supermarkets, apartment buildings, hotels, and coin-parkings will maintain high capacity stationary batteries. Power supply from a power grid and power price can vary in the course of a day. Hereinafter, charging facilities provided at service stations, office buildings, plants, supermarkets, apartment buildings, hotels, convenience stores, and coin-parkings will be referred to as charging stations.
Due to limitation in available power from a power grid, charging and discharging rates of batteries, and different departure times, EVs waiting at a charging station (i.e., EVs in a queue) cannot be charged at the same charging rate. Additionally, because the arrival of EVs at a charging station located such as at a supermarket, convenience store, coin-parking center is virtually probabilistic, all energy from a stationary battery cannot be used for charging the EVs in a queue when a fair use policy is applied. In this case, prediction of future power requirement for the EVs is necessary. It is required to adjust the charging rate for EVs that have arrived in accordance with predicted power requirement for EVs in the next time range and the departure time of the EVs. Thus, dynamic scheduling for EV charging at a charging station will be required in future.
When using a fair use policy, it is desirable to determine charging energy that can be supplied to the EVs waiting at a charging station in consideration of EVs that are possible in the next time range. It is also desired to schedule charging of waiting EVs so as to meet many constraints, such as the electric power available from a grid at each time of a day, power from a stationary battery, maximum charging and discharging rates of batteries, and departure time of waiting EVs (i.e., time of use).